It’s the subjective element of Stand Your Ground laws that makes them come out racist. Any self-defense case involves a tragedy – but when convictions turn on the killer’s subjective impression of who is threatening, the people who get killed are more likely to belong to racial minorities and other out-groups, including people with disabilities.

Human encounters are affected by social distance, a measure of relatedness, a bundle of concepts ranging from familiar, approved, trustworthy and safe, to strange, different, suspicious and unsafe. People are said to be closest to those they trust and know best, typically those who are most like them. Social distance can be seen today playing out in a benign fashion in restaurants, stadiums and other public spaces. More people gather in same-group clusters than in more diverse clusters, even when everyone in the larger setting abides peacefully and even shares interests, attitudes, educational background and motivation for gathering.

The notion of relative safety connected with one’s own family and tribe, and higher perceived risk when encountering strangers, is an artifact of human evolution built into DNA and human nature.

From our earliest moments, we construct mental models, learning who is safe, who to avoid, and how to obtain what we need. We develop and rely on patterns, lumping similar things (or similar types of people) together. Mental models are working theories of the world, approximations of what we have learned, that incorporate what we see and hear from others as well as what we experience ourselves. Mental models connected to social distance may be useful and accurate, or dead wrong. Fortunately, mental models are subject to revision as we get to know people, and as we learn and navigate the world.

Social distance becomes embodied in social policies and plays out in individual actions. No one is immune to its effects. In American society we are expected to manage and adjust our mental models so raw prejudice doesn’t cloud our judgment or taint our actions. Each generation tends to do better at this. However, Stand Your Ground laws validate prejudice and social distance, giving everyone a license to kill.

Consider how social distance has affected people with disabilities. Human society has always included people who could not see, walk or hear, and people with limited mobility, intellect or other reduced functioning, yet the concept of disability as a phenomenon that might itself be studied or discussed arrived relatively recently to Western society, in the mid-19th century. People initially spoke of conditions that were “natural” or “normal” and contrasted these with what was considered “monstrous” or “defective.” As scientists cataloged the variations in people’s bodies and capacities, they made judgments about the value of the lives of the people they studied. In the 19th century, as the theory of evolution mixed with the era’s crude racial stereotypes, researchers began to describe both nonwhite races and disabled people as regressions or throwbacks. For example, the physician who first identified Down Syndrome called it Mongolism because he understood it as a biological reversion by Caucasians to the Mongol racial type. This mode of thought, called Social Darwinism, set the stage for the eugenics movement and the Nazi Holocaust, and also played a role in immigration laws that forbade entry both to members of ethnic groups thought to be prone to criminality or deformity and to people with mental or physical defects. The mission of state institutions for people with mental illness and developmental disabilities also changed. Promoted in the 1840s as moral reforms, by the early 20th century the institutions were more frequently described as a means of social control. They kept members of productive society safe and separated ordinary citizens from those now described as sub-normal. People receiving care in these institutions suffered a type of social death.

Even today, disability connects with stigma, an “attribute that is deeply discrediting” and that reduces the bearer “from a whole and usual person to a tainted, discounted one” in the words of sociologist Erving Goffman. Stigma originates from a process that involves labeling, linking to negative stereotypes, separation of “us” from “them”, and status loss and discrimination that leads to unequal outcomes.

Ultimately, stigma leads to partial or complete disempowerment, and now, even increased risk of death. The rhetoric of the gun lobby is doubly disturbing to disability advocates. We see people encouraged both to fear people with mental illness and "stand their ground" against whoever is perceived as threatening.